Magnet operated switch



June 5, 1951 A. E. CHISHOLM MAGNET OPERATED swITcH Filed June 11, 1948 2 Sheets-Sheet. 1

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June 1951 A. E. CHISHOLM 5,

MAGNET OPERATED SWITCH Filed June 11, 1948 2 Sheets-Sheet 2 T %M@ '8 9 2213 f i. .5. T a INVENTOR.

/44 4.5m 5 6/l/5HOLM ATTORNEY Patented June 5, 1951 UNITED STATES PATENT OFFICE MAGNET OPERATED SWITCH Allen E. Chisholm, Portland, Oreg.

Application June 11, 1948, Serial No. 32,470

9 Claims. 1 This invention is of a magnet operated double snap action electrical switch. The switch snaps open, snaps closed, and, unlike the familiar spring snapover, it has no dead point.

The objects of this invention are to produce the double snap action recited supra.

A further object is to produce a switch that is believed to be much faster acting than previous switches.

Another object is to produce a switch having the qualities stated together with the ability to use a wide air gap between switch contacts when the switch opens, to increase the ability to break heavy currents, without a relay.

Another object is superior sensitivity, in that the movement of the magnet that closes the switch, may be of exceedingly small amount, thus practically eliminating lag in controls of many varieties of apparatus, especially in processes requiring exceedingly close temperature regulation. These and almost innumerable objects long desired by technical engineers will be at once apparent from the disclosure, the novel features of which are pointed out in the claims.

' Drawings accompany and form a part of this specification, in which:

- Fig. 1 is a side view of an anemometer with a modification of the invention for translating steps of velocity into electrical currents, as for example when it is desired to signal velocity to the pilot of a plane, aloft;

Fig. 2 is a section taken on the plane 2-2 Fig. 3 is a plan view of the magnet switch of the invention with a part broken away to show the switch contact;

' Fig. 4 is a section taken on the plane I4, Fig. 3; and

Fig. 5 is an elevation showing the magnet switch from one side.

Explaining the drawings in greater detail:

In Fig. 1, a cup anemometer I revolves a vertical shaft 2, in the well known manner. A weatherproof case 3 contains means for sending electrical impulses controlled by five difierent and independent electrical switches according to the invention as hereinafter explained, numbered 4, 5, 6, I and 8, through the wires 24, for signaling purposes.

The several switches, 4 to 8 inclusive, are operated by a magnet 9, on the end of the lever III, which is movable arcuately by the fly-ball governor mechanism II, believed to be so well known and universally used for the identical purpose that no explanation of the mechanism is necessary. The governor II is operated by the anemometer I, and will correctly correspond to wind velocity. Here it is to be noted that the magnetic pull is axial of the lever I0, without drag.

The lever IOwith its magnet 9 is registering scribed in detail with respect to the showing in Figs. 3, 4 and 5.

A block of insulating materal I2, supports a switch frame I3, by screws I4, one of which is v shown to constitute a terminal I5 for an electrical circuit member. The other member of the circuit may be attached to the terminal I6, which is electrically continuous with the switch contact IT, the same bein electrically discontinuous with the frame I3, by air gaps such as I8. A switch blade I9, is shown clamped in the clamp 20 of the frame I3, to be electrically continuous therewith and at its free end, opposite, it has the switch contact 2I arranged directly in registry with contact Il, when the two are brought together. The blade I9, in this case, is made of non-ferrous sprin material such as spring bronze. In its median portion is an armature 22 of steel or the like, sensitive to magnetic influence of the magnet 23 which will be relatively positioned with respect to the armature 22.

. bias tending to complete the contact between contacts I! and 2 I.

However, the magnet 23 in Fig. 4, being uninfluenced by magnet 9 on account of the width of the air gap, has overcome the spring bias and opened the switch. When the magnet 9 is brought closer and confronts magnet 9, as is done in Figs. 1 and 2, the springiness of the switch blade I9, plus the magnetic pull of the magnet 9, snaps the switch shut.

The snap action, being a part of the principle of the invention, is due to that inherent characteristic of a magnet, that its pull is inversely as the square of the air gap width, thus when the magnet 9 approaches the armature 22, it finally starts the armature towards it, the gap narrows, the power is greatly increased and the switch blade moves exceedingly fast. When the magnet 9, begins to increase the air gap between itself and the armature, the pull decreases as the square of the gained distance and another very 3 fast action takes place when magnet 23 takes over.

It will be seen that this switch is positive. When the actuating magnet reaches close enough to the armature to move it, ever so slightly, its own power is greatly increased and at the same time the power of the relatively fixed magnet is impaired at the same ratio; hence the exceedingly fast action; and it will easily be understood that difference in placement of say .001" can determine whether the switch stays open or shuts with a snap. It will be at once noted, also, that by proportionately lengthening that part of the blade that carries the contacts such as I! and 2 I, there will be increased sensitivity to forces tending to move magnet 9 if those forces are applied nearer to the spring 3|.

Where it is not expedient to do so, the switch may be made without the spring bias, relying on the magnet 23 to hold it normally open. Modern alloy magnets are preferred in apparatus of the sort as they are practically permanent and offer many advantages over a wound electromagnet. It is not, however, intended to exclude the latter as the principle of the invention would be unchanged by their substitution.

, In Figs. 4 to 6 inclusive, the magnet 9 is mounted on a lever 30 and that is attached to a springy mounting 3|, there being a stop 32, to prevent complete closure of the air gap 25, which, like air gap 33, must always have some value. The delineation here is schematic as the invention does not operate well without maintenance of these air gaps.

Having fully explained my invention so that those familiar with the art to which it appertains can make and use it, what I claim as new and desire to secure by Letters Patent, is:

1. A double snap action switch for electrical circuit work comprising a switch blade movable to control a circuit, an armature mounted on said blade between the ends thereof, said blade biased to normal switch closing position, a relatively fixed magnet positioned to overcome the bias and hold the switch open with an air gap between said magnet and said armature, a switch closing magnet mounted for movement relative to said armature to overcome said first named magnet and close the switch, said movable magnet mounted to move into and out of position confronting said fixed magnet with said armature therebetween.

2. An electrical snap switch comprising a blade biased to close a pair of switch contacts, an armature mounted on said blade, contacts therefor, one being mounted on said blade, a relatively fixed magnet positioned to pull saidswitch open, over the bias by pull on said armature, and a switch operating magnet mounted for reverse movement in a predetermined path to a position opposite said fixed magnet, effective to overcome said first magnet, upon close approach to said armature and close the switch.

3. An electrical snap switch, comprising a cur- 4. An electrical snap switch, comprising in combination a switch operating blade, an armature carriedby saidblade; a relatively fixed mag- 4 net, with an air gap spacing it from said armature, that holds the switch normally open, and an operating magnet movable with respect to said armature into confronting position on the opposite side of said armature from said first named magnet and closing the switch.

5. An electrical snap switch, comprising in combination a switch operating blade, an armature carried by said blade, a relatively fixed magnet with an air gap spacing it from said armawire, that holds the switch normally open, and an operating magnet movable in a fixed path with respect to said armature into and out of confronting position with respect to said first named magnet, with said armature between the poles of the magnets.

6. An electrical snap switch, comprising in combination a switch operating blade, an armature carried by said blade, a biasing means therefor that tends to close the switch, a relatively fixed magnet with an air gap spacing it from said armature, that holds the switch normally open, and an operating magnet movable into confronting position to said first magnet with said armature therebetween which upon close approach, overcomes said first named magnet and with the assistance of said biasing means closes the switch.

7. A magnet operable electrical circuit switch, comprising fixed and movable circuit contact members, an armature operably connected to said movable member, a magnet positioned to bias said movable member by pull on said armature to predetermined relationship to said fixed memher and a movable magnet arranged to approach said armature to a position opposite said first named magnet, to overcome the same and reverse said circuit contact members.

8. A magnet operable electrical circuit switch, comprising fixedand movable circuit contact members, an armature incorporated with said movable member, a magnet positioned to bias said movable member by pull on said armature to predetermined relationship to said fixed member and a movable magnet arranged to approach said armature to a position opposite said first named magnet, to overcome the same and reverse said circuit contact members.

9. A sensitive electrical switch comprising amovable current carrying blade, an armature mounted on said blade, a relatively fixed magnet spaced by an air gap from said armature that biases said blade in a predetermined position and a control magnet movable towards and from confronting position on the opposite side of said armature, which upon close approach thereto overcomes the first named magnet and reverses the position of said blade.

ALLEN E. CHISHOLM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Re. 21,038 Leins Mar. 28, 1939 1,348,842 Barlow Aug. 10, 1920 2,004,114 Hubbell, Jr. June 11', 1935 2,264,058 Vigren et a1 Nov. 25, 1941 2,289,830 Ellwood July 14, 1942 2,323,910 Hubbell July 13, 1943 2,355,894 Ray Aug. 15, 1944 2,439,121 Adelson Apr. 6, 1948 Reaivis 

